The present invention relates to a dot matrix printing head and more particularly to a printing head comprising a generally circular array of bucking-coil, stylus drivers capable of printing 1000 characters per second or more.
The use of bucking coil stylus drivers in printing heads is known in the art; such an arrangement being currently employed in the Printronix 300 dot matrix printer and having been previously employed in character printers.
Problems with the prior art bucking coil printers arise when it is desired to greatly increase the cyclic rate of operation of the drivers beyond that which such devices currently provide. For instance, the permanent magnets employed in the prior art devices do not produce sufficient flux density to permit operation at the speeds contemplated by the present invention and when magnets of sufficient strength are employed the weight is increased and the leakage flux becomes so great that proper operation may not be achieved.
Further, an increase in the strength of the permanent magnet dictates a large increase in the strength of the bucking coil resulting in severe problems of heat dissipation and cross-talk between adjacent drivers. In addition, the overall physical structures of the prior art devices are such as to cause, at high speeds of operation, severe inertia problems and twisting, flexing and whipping of various elements; all of which at the least greatly increase the energy required to operate the system and at the worst prevent such operation or severely reduce the life of the apparatus.